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Checking in development gaskets against BBMs

February 12 2018 at 11:05 AM
Marc H  (Select Login turbohunter)

There's a thread below where Chillymerc was asking about gaskets for a refresh he's doing.
Ross brought up that SCE has a new set out. The owner of SCE is my brother Ryan. He was doing me a favor and built a gasket for street use that tried to cut down on oil control problems and didn't give away volume between the head and block by being to large a bore size for us smaller bore guys. I gave a couple gaskets out to a couple guys one being Ross so they could take a look at them. Business crap like moving the plant out of California got in the way so it's taken a while to get back to it. So Chilly's thread was well timed.
The gasket is composite with a new coating that has strong anti capillary properties and is supposed to be pretty cool. The center is steel as well as a thick stainless fire ring. We/I wanted to make the bore size 4.250. The only problem with that, that Ross brought up to me is that heads are built so that the chamber is quite a bit wider than the cylinder of smaller bore engines. So the top of the fire ring on iron heads is partially unsupported on the head side.
I slapped together my truck engine with the first set of gaskets. It is a 4.125 bore by 4.125 stroke D4TE with D2 heads. D2 heads leave a bit of the fire ring unsupported. I haven't had a lick of trouble with it for years now. Not saying that's the right way to do it, I offer it up just for info.
So enough background. Chilly is looking to run BBMs on his freshen up so after some discussion I went over to BBM which is close to me and checked out the fit. Pics below.
So Chilly may not want to run these gaskets because he has some squish issues to deal with but I would love to get some comment from you builders about bore size and gasket fit. Is the volume given away by a larger bore gasket anywhere close to the problem that improper quench is? I don't have near the experience you guys do. My brother is planning to make the gaskets thinner in the future and indeed the newer gasket I have in my garage is a bit thinner but still a ways to go. A larger bore is coming one day also. He's also doing some fire ring experimentation.
Happy to hear any and all comments.
[linked image][linked image]

This message has been edited by turbohunter on Feb 12, 2018 2:18 PM

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Blair Patrick
(Login CaptCobrajet)

Looks pretty good to me......

February 12 2018, 2:56 PM 

on the BBM as-cast. It also appears to be round, which I think is a plus. There isn't much volume lost to a bigger bore. It is mostly the thickness that makes volume and of course hurts quench in the process. I think a 4.350 "round" would work on almost all FEs. Only bores over 4.320 with really "massaged" chambers would need anything larger. Just my .02.....
Blair Patrick

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(Login Barry_R)

I would go a hair bigger

February 14 2018, 8:57 AM 

Since the Shelby blocks and aftermarket iron end up at 4.375 bore fairly often - that would be my reference bore ID for the fire ring. Not all that much crevice volume loss when the ring is .060 away from the bore edge on smaller stuff - but you do need to support the fire ring.
Barry Rabotnick

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Tom P
(Login tomposthuma)

fire ring

February 14 2018, 8:35 PM 

Would it be a big issue to have the fire ring flush or slightly into the bore with a chamber that fits in the ring? Or is that asking for a blown head gasket?

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(Login Bad427stang)

My opinion

February 15 2018, 4:36 AM 

IMO Having the fire ring hanging out allows a hot spot out that could lead to failure, maybe detonation and then failure, but really I am worried about seal and heat transfer.

Having the fire ring supported allows heat transfer to block and head, so the relatively thin ring doesn't hold all the heat.

Flush after crush wouldn't bother me, in fact, I think it would be good if it has full contact on both sides. The problem is, that these chambers tend to be larger than 4.08, so you have to match the head, not the cylinder bore

So if I understand your question "If it does have full contact on both sides, can it hang over?" I don't really like it, but depending on how far it hangs over, it should wick the heat away. Another issue there is we chase every bit of airflow, and you are now adding a lip along the cylinder wall below the valve, I wouldn't want that either.
[linked image]
- 70 Fastback Mustang, 489 cid FE, Victor, SEFI, TKO-600 5 speed, 4.11 9 inch.
- 71 F100 shortbed 4x4, 445 cid FE, headers, RPM intake, 1000 HP series Holley, 4 speed

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